What I would recommend, especially over an open Wi-Fi connection, is trying to use secure (i.e. https) web pages for logging in and even for reading private email. GMail, PPRuNe mail, Yahoo etc. all allow you to log in securely, but only GMail (off the top of my head) then keeps the https connection. The login URL is stable which means it can be bookmarked.
And ClamAV is the first MacOS AV software which appeared when I googled it. Ping me in a month and I might know more about it
